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Potentiometers for Preamps - Which is Best?
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Author:  Suncalc [ 20 Jun 2011, 20:38 ]
Post subject:  Potentiometers for Preamps - Which is Best?

All;

I am looking at designing a "coloring" preamp which I can use to adjust the overall sound volume, tone, balance, and even order distortion. But the design is going to require at least three (maybe four) potentiometers per channel. So to keep it quiet, I need to know what are the best potentiometers out there. I'd like to keep it under $20 each if possible but I could spend more if they really are good units.

Everybody chime in.

Thanks.
Matt

Author:  Gio [ 20 Jun 2011, 21:04 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

I'll toss my vote in for Alps Blue Velvet. These are conductive plastic types and great quality. You can get them for about $15-$20.

Cheers

Author:  Geek [ 20 Jun 2011, 21:25 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

Careful - there are more Blue Velvet counterfeits than you can shake a stick at and the only way to tell is to take 'em apart :-\
(If you have a source for real ones under $30, I'd be happy to know!!!)

I'm hooked on these:
http://search.digikey.com/scripts/DkSea ... 1041S28-ND

Not cheap, but made local and couterfeitting is non existant.

Cheers!

Author:  Suncalc [ 20 Jun 2011, 22:00 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

I assume that when you say "Alps Blue Velvet" you're talking about the Alps RK27 series potentiometer? Correct? Or do you mean the RK50 series?

Author:  cheap-Jack [ 21 Jun 2011, 08:29 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

Hi
Gio wrote:
I'll toss my vote in for Alps Blue Velvet.

Bingo, I second. :thumbsup: I mean RK27112 - Affordable but worth every penny spent on it.
Geek wrote:
there are more Blue Velvet counterfeits than you can shake a stick at

Too true. Faked Alps RK27112 looks virtually identical to the real one (made in Japan), but only the terminals are different - standard round lugs with hole like any no-name pots, instead of pins. I think they are faked from China.

c-J
PS: I am not going to spend a few hundred bucks for a volume control! :!:

Author:  Geek [ 21 Jun 2011, 16:22 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

cheap-Jack wrote:
...but only the terminals are different - standard round lugs with hole like any no-name pots, instead of pins. I think they are faked from China.

Or Taiwan....

I came across a fake with identical pins to the real one except the case edges were really rough (letting gunk in). I opened it up and conductive plastic my foot! The wafers were carbon-clad (none too good either, some wiped off with my finger) and that and the wipers interestingly identical to an Alpha.

maybe the fakers are at least getting custom parts from Alpha (I can't see Alpha being the culprit)?

Cheers!

Author:  Gio [ 21 Jun 2011, 17:39 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

Geek wrote:
Careful - there are more Blue Velvet counterfeits than you can shake a stick at and the only way to tell is to take 'em apart :-\ (If you have a source for real ones under $30, I'd be happy to know!!!)

I should be careful with the "Blue Velvet" terminology. These are the Blue conductive plastic Alps pots that I am talking about: http://www.partsconnexion.com/controls_pot_alps.html (note that pCx is located in Canada). The Alps pots are original as far as I can tell. If someone has a link or photo that shows the fake post, please post. I've only tried the 50k and 100K pots, $17.95. I've made about 6 purchases with pCx over the past few years with no problems.

Cheers

Author:  Suncalc [ 21 Jun 2011, 17:55 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

Well those certainly look like these at Mouser (http://www.mouser.com/ProductDetail/ALPS/RK27112A-S20-C0-A104/?qs=sGAEpiMZZMsEGgLEzQVydhmUlsXMQ%252bUQFH25Lv5hWAU%3d) but it's difficult to be sure. The manufacturer part numbers at Mouser match those at the Apls website, the ones at Parts Connection (537G?) I don't find on the Alps site.

So what makes these Alps so nice? Is it just feel? Or is it noise level, lifetime, performance, etc? What makes them better than other manufacturer's cermet pots? I'm curious.

Author:  Gio [ 21 Jun 2011, 18:39 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

I am looking at one and it is marked with only:
ALPS JAPAN
705G 100KAX2

I like the feel and have never any noise problems in about 4-5 years of using them. I think these pots will have a very long life. They have already out lived a lot of carbon pots.

Is "Conductive Plastic" the same as cermet?

Cheers

Author:  Suncalc [ 21 Jun 2011, 18:52 ]
Post subject:  Re: Potentiometers for Preamps - Which is Best?

Sorry, old habit. I've been design military gear far too long.

"Cermet" is actually a ceramic-metalic pot of very precise operation. They are capable of precisely holding a setting for many years. They are generally used for trimmers and internal equipment adjustments. They actually have a very short "cycle lifetime".

You are correct, we are actually talking about "conductive plastic" here. Not nearly as precise as cermet but they have a long "cycle lifetime" and much lower noise than carbon (either basic composition or hot molded).

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